Let S be a compact, connected, oriented surface, possibly with boundary, of negative Euler characteristic. In this article we extend Lindenstrauss-Mirzakhani's and Hamenstädt's classification of locally finite mapping class group invariant ergodic measures on the space of measured laminations ML (S) to the space of geodesic currents C (S), and we discuss the homogeneous case. Moreover, we extend Lindenstrauss-Mirzakhani's classification of orbit closures to C (S). Our argument relies on their results and on the decomposition of a current into a sum of three currents with isotopically disjoint supports: a measured lamination without closed leaves, a simple multi-curve and a current that binds its hull.Résumé. -Soit S une surface compacte, connexe, orientée, éventuellement à bord, de caractéristique d'Euler négative. Dans cet article nous étendons la classification des mesures ergodiques, localement finies et invariantes sous l'action du mapping class group, sur l'espace des laminations mesurées ML (S) obtenue par Lindenstrauss-Mirzakhani et Hamenstädt, à l'espace des courants géodésiques C (S), et nous discutons le cas homogène. De plus, nous étendons la classification de la fermeture des orbites obtenue par Lindenstrauss-Mirzakhani à C (S). Notre argument repose sur leurs résultats et sur le décomposition d'un courant en une somme de trois courants avec supports isotopiquement disjoints: une lamnation mesurée sans feuilles fermées, une multi-courbe simple et un courant qui remplit son enveloppe.
Viveka ERLANDSSON & Gabriele MONDELLO
SettingLet S be a smooth, compact, connected, oriented surface of negative Euler characteristic, possibly with boundary, and let Map(S) be its mapping class group, i.e. the group of isotopy classes of orientation-preserving diffeomorphisms S → S that send each boundary curve of S to itself.Consider an auxiliary hyperbolic metric on S such that ∂S is geodesic. A geodesic current on S is a π 1 (S)-invariant Radon measure on the space G( S) of bi-infinite geodesics in the universal cover S of S. The space C (S) of all geodesic currents, naturally endowed with the weak -topology, can also be viewed as the completion of the set of weighted closed curves on S in the same way as the space ML (S) of measured laminations is the completion of the set of weighted simple closed curves. Recall that a measured lamination is a closed subset of S foliated by complete geodesics and endowed with a transverse measure of full support. Hence a measured lamination can be viewed as a current and ML (S) can be viewed as a subspace of C (S). The geometric intersection number of closed curves has a unique continuous extension to a symmetric, bi-homogenous intersection form). The subspace of measured laminations consists exactly of those currents c for which ι(c, c) = 0.The aim of this paper is to provide a classification of locally finite ergodic measures on C (S) that are invariant under the natural action of Map(S) and of closures of Map(S)-orbits on C (S).
MotivationThe impetus for the present paper -in add...